Organic light emission diode (OLED) has been widely used as a current-source-based light emitter for high performance display equipment. Specifically, in active matrix OLED display, each row of an array of pixels is sequentially turned on by progressively scanning through row-by-row for display. A data voltage is applied to every row of pixels that is turned on, based on which an OLED current is generated to cause the diodes in the row of pixels to emit light for displaying an image controlled by the data voltage.